Plastic container having improved flexible panel

ABSTRACT

A plastic container that is adapted for adjustment to internal volumetric changes such as those that typically occur during the hot fill process includes a container body defining an internal space. The container body has a sidewall that is shaped to define at least one flexible panel. The flexible panel has a central longitudinal axis, an upper portion, a lower portion and a central portion. The central portion of the flexible panel has a width that is greater than a respective width of at least one of the upper and lower portions. The flexible panel is substantially flat as viewed in a longitudinal cross-section taken along the central longitudinal axis. Additionally, the central portion has a transverse radius of curvature that is greater than a transverse radius of curvature of at least one of the upper portion and said lower portion. Because the central portion represents the maximum width of the flexible panel, the efficiency of vacuum uptake is maximized with respect to conventional vacuum panels that are substantially flat in longitudinal cross-section.

BACKGROUND OF THE INVENTION

1.Field of the Invention

This invention relates generally to the field of plastic containers, and more particularly to plastic containers that are designed to accommodate volumetric expansion and contraction such as that inherent to the hot-fill packaging process or to packaging applications where internal pressurization is anticipated.

2. Description of the Related Technology

Many products that were previously packaged using glass containers are now being supplied in plastic containers, such as containers that are fabricated from polyesters such as polyethylene terephthalate (PET).

PET containers are typically manufactured using the stretch blow molding process. This involves the use of a preform that is injection molded into a shape that facilitates distribution of the plastic material within the preform into the desired final shape of the container. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it takes on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold.

Hot fill containers are designed to be used with the conventional hot fill process in which a liquid or semi-solid product such as fruit juice, sauce, salsa, jelly or fruit salad is introduced into the container while warm or hot, as appropriate, for sanitary packaging of the product. After filling, such containers undergo significant volumetric shrinkage as a result of the cooling of the product within the sealed container. Hot fill type containers accordingly must be designed to have the capability of accommodating such shrinkage. Typically this has been done by incorporating one or more vacuum panels into the side wall of the container that are designed to flex inwardly as the volume of the product within the container decreases as a result of cooling.

Typically, the vacuum panel regions of conventional hot fill containers are characterized by having surfaces that are designed to deflect inwardly when the product within the sealed container undergoes shrinkage. The amount of volumetric contraction, also referred to as vacuum uptake, that can be provided by a conventional vacuum panel is limited by the size of the panel. The design of such containers is often influenced by the aesthetic preferences of manufacturers, which in some instances can limit the size of the vacuum panels to the extent that makes it difficult or impossible to achieve the necessary vacuum uptake capacity.

A need therefore exists for an improved vacuum panel configuration that achieves a maximal amount of vacuum uptake capacity in relation to the size of the vacuum panel.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a plastic container having an improved vacuum panel configuration that achieves a maximal amount of vacuum uptake capacity in relation to the size of the vacuum panel.

In order to achieve the above and other objects of the invention, a plastic container according to a first aspect of the invention that is adapted for adjustment to internal volumetric changes such as those that occur during the hot fill process includes a container body defining an internal space. The container body has a sidewall that is shaped to define at least one flexible panel. The flexible panel has a central longitudinal axis, an upper portion, a lower portion and a central portion. The central portion of the flexible panel has a width that is greater than a respective width of at least one of the upper and lower portions. The flexible panel is substantially flat as viewed in a longitudinal cross-section taken along the central longitudinal axis.

A plastic container according to a second aspect of the invention is adapted for adjustment to internal volumetric changes such as those that occur during the hot fill process includes a container body defining an internal space. The container body has a sidewall that is shaped to define at least one flexible panel. The flexible panel has a central longitudinal axis, an upper portion, a lower portion and a central portion. The central portion of the flexible panel has a width that is greater than a respective width of at least one of the upper and lower portions. The central portion has a transverse radius of curvature that is greater than a transverse radius of curvature of at least one of the upper portion and said lower portion.

These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a plastic container that is constructed according to a preferred embodiment of the invention;

FIG. 2 is a side elevational view of the plastic container that is depicted in FIG. 1;

FIG. 3 is a cross-sectional view taken along lines 3-3 in FIG. 1;

FIG. 4 is a cross-sectional view taken along lines 4-4 in FIG. 2;

FIG. 5 is a cross-sectional view taken along lines 5-5 in FIG. 2;

FIG. 6 is a cross-sectional view taken along lines 6-6 in FIG. 2;

FIG. 7 is a cross-sectional view taken along lines 7-7 in FIG. 2; and

FIG. 8 is a cross-sectional view taken along lines 8-8 in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to FIG. 1, a plastic container 10 that is constructed according to a preferred embodiment of the invention is preferably fabricated according to the conventional reheat stretch blow molding process from a material such as polyethylene terephthalate, which is commonly known by the acronym PET.

Plastic container 10 preferably includes a bottom portion 12, a main body portion 14 and an upper portion including a tapered dome or bell 16 and a threaded finish portion 18. The entire container 10 is formed from a thin sidewall 15 that defines an internal space within the container 10.

The portion of the sidewall 15 that forms the main body portion 14 is shaped to define a first substantially rigid sidewall portion 20 that is reinforced with a plurality of substantially horizontally oriented inwardly extending grooves 22. Main body portion 14 also includes a second substantially rigid sidewall portion 24 that is reinforced with a plurality of substantially horizontally oriented inwardly extending grooves 26. First and second flexible panel portions 28, 40 are interposed between the first and second rigid sidewall portions 20, 24 around the circumference of the main body portion 14, as is shown in FIGS. 1-3.

The first and second flexible panel portions 28, 40 are preferably of identical size and shape, so further description that is made of the first flexible panel portion 28 applies equally to the second flexible panel portion 40. The flexible panel 28 is preferably elongated about a central longitudinal axis 30, as is best shown in FIG. 1, and includes a central portion 32 including a longitudinal center point 34, an upper portion 36 and a lower portion 38. The central portion 32 of the flexible panel 28 preferably has a width that is greater than a respective width of at least one of the upper and lower portions 36, 38. In the preferred embodiment, the central portion 32 has a width that is greater than the respective widths of both of the upper and lower portions 36, 38.

In the preferred embodiment, flexible panel 28 is substantially oval in shape as viewed in side elevation, as is best shown in FIG. 1. Flexible panel 28 is also preferably is convexly curved in transverse cross-section, as is best shown in FIGS. 4-8. In addition, as is best shown in FIG. 3, flexible panel 28 is shaped so as to be substantially flat, with no projections or raised portions, as viewed in a longitudinal cross-section taken along the central longitudinal axis 30.

Preferably, the central portion 32 of the flexible panel 28 has a transverse radius of curvature that is greater than a transverse radius of curvature of at least one of the upper portion 36 and the lower portion 38.

FIG. 4 is a cross-sectional view taken at an extreme upper end of the flexible panel 28, at which the flexible panel 28 has a first transverse radius of curvature R₁. The flexible panel 28 preferably has a first width W₁ at this location that is a minimum width for the entire flexible panel 28. A ratio of first width W₁ to the first transverse radius of curvature R₁ is preferably within a range of about 0.2 to about 1.0, and more preferably within a range of about 0.4 to about 0.8. Most preferably, the ratio of first width W₁ to the first transverse radius of curvature R₁ is within a range of about 0.55 to about 0.74.

FIG. 5 is a cross-sectional view taken within the upper portion 36 of the flexible panel 28, at which the flexible panel 28 has a second transverse radius of curvature R₂ that is preferably greater than the first transverse radius of curvature R1. The flexible panel 28 preferably has a second width W₂ at this location that is preferably greater than the first width W₁. A ratio of second width W₂ to the second transverse radius of curvature R₂ is preferably within a range of about 0.2 to about 1.0, and more preferably within a range of about 0.4 to about 0.8. Most preferably, the ratio of second width W₂ to the second transverse radius of curvature R₂ is within a range of about 0.55 to about 0.74.

FIG. 6 is a cross-sectional view taken through the longitudinal center point 34 of the central portion 32 of the flexible panel 28, at which the flexible panel 28 has a third transverse radius of curvature R₃ that is preferably greater than either of the first and second radii of curvature R₁, R₂. The third transverse radius of curvature R₃ is preferably a maximum transverse radius of curvature within the flexible panel 28. The flexible panel 28 preferably has a third width W₃ at this location that is preferably a maximum width for the entire flexible panel 28. A ratio of third width W₃ to the third transverse radius of curvature R₃ is preferably within a range of about 0.2 to about 1.0, and more preferably within a range of about 0.4 to about 0.8. Most preferably, the ratio of third width W₃ to the third transverse radius of curvature R₃ is within a range of about 0.55 to about 0.74.

FIG. 7 is a cross-sectional view taken through the lower portion 38 of the flexible panel 28, at which the flexible panel 28 has a fourth transverse radius of curvature R₄ that is preferably less than the third transverse radius of curvature R₃. A flexible panel 28 preferably has a fourth width W₄ at this location that is less than the third width W₃. A ratio of fourth width W₄ to the fourth transverse radius of curvature R₄ is preferably within a range of about 0.2 to about 1.0, and more preferably within a range of about 0.4 to about 0.8. Most preferably, the ratio of fourth width W₄ to the fourth transverse radius of curvature R₄ is within a range of about 0.55 to about 0.65.

Preferably, the respective ratios of the width of the flexible panel 28 to the transverse radius of curvature for the locations that are shown in FIGS. 4-7 are substantially equal.

FIG. 8 is a cross-sectional view taken through an extreme bottom end of the flexible panel 28, at which the flexible panel 28 has a fifth transverse radius of curvature R₅ that is preferably less than either the third or fourth radii of curvature R₃, R₄. The flexible panel 28 preferably has a fifth width W₅ at this location that is less than the third and fourth widths W₃, W₄ and that is preferably equal to a minimum width for the entire panel 28. A ratio of fifth width W₅ to the fifth transverse radius of curvature R₅ is preferably within a range of about 0.1 to about 1.0, and more preferably within a range of about 0.15 to about 0.8. Most preferably, the ratio of fifth width W₅ to the fifth transverse radius of curvature R₅ is within a range of about 0.25 to about 0.45.

In operation, the central portion 32 of the flexible panel 28 deflects to a greater extent while absorbing vacuum uptake than do the upper and lower portions 36, 38. Because the central portion 32 represents the maximum width of the flexible panel 28, the efficiency of vacuum uptake is maximized with respect to conventional vacuum panels that are substantially flat in longitudinal cross-section.

The flexible panel 28 is constructed so that the convexity of the central portion 32 and the upper and lower portions 36, 38 is reduced when accommodating vacuum uptake. Flexible panel 28 may be constructed so that it inverts during vacuum uptake from the unstressed convex curvature described above to a concave curvature, or it may be constructed so that it remains convex, with the degree of convexity reduced when there is volumetric shrinkage within the container 10.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A plastic container that is adapted for adjustment to internal volumetric changes, comprising: a container body defining an internal space, said container body having a sidewall comprising at least one flexible panel defining a central longitudinal axis, said flexible panel having an upper portion, a lower portion and a central portion; said central portion of said flexible panel having a width that is greater than a respective width of at least one of said upper and lower portions; and wherein said flexible panel is substantially flat as viewed in a longitudinal cross-section taken along said central longitudinal axis.
 2. A plastic container according to claim 1, wherein said flexible panel is substantially oval-shaped as viewed in side elevation.
 3. A plastic container according to claim 1, wherein said flexible panel is convexly curved.
 4. A plastic container according to claim 1, wherein said central portion has a transverse radius of curvature that is greater than a transverse radius of curvature of at least one of said upper portion and said lower portion.
 5. A plastic container according to claim 1, wherein said central portion has a width that is greater than respective widths of both said upper portion and said lower portion.
 6. A plastic container according to claim 1, wherein said flexible panel is elongated along said central longitudinal axis.
 7. A plastic container according to claim 1, wherein said central portion of said flexible panel has a longitudinal center point, and a first transverse radius of curvature taken through said longitudinal center point, and wherein said first transverse radius of curvature is a maximum transverse radius of curvature within said flexible panel.
 8. A plastic container that is adapted for adjustment to internal volumetric changes, comprising: a container body defining an internal space, said container body having a sidewall comprising at least one flexible panel defining a central longitudinal axis, said flexible panel having an upper portion, a lower portion and a central portion; said central portion of said flexible panel having a width that is greater than a respective width of at least one of said upper and lower portions; and wherein said central portion has a transverse radius of curvature that is greater than a transverse radius of curvature of at least one of said upper portion and said lower portion.
 9. A plastic container according to claim 8, wherein said flexible panel is substantially oval-shaped as viewed in side elevation.
 10. A plastic container according to claim 8, wherein said flexible panel is convexly curved.
 11. A plastic container according to claim 8, wherein said central portion has a width that is greater than respective widths of both said upper portion and said lower portion.
 12. A plastic container according to claim 8, wherein said flexible panel is elongated along said central longitudinal axis.
 13. A plastic container according to claim 8, wherein said central portion of said flexible panel has a longitudinal center point, and a first transverse radius of curvature taken through said longitudinal center point, and wherein said first transverse radius of curvature is a maximum transverse radius of curvature within said flexible panel. 